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HARD WICKE » S S CIENCE - G O SSI P. 



" The author gives the following recipe for a cement 

 to be used for fixing the covers on glycerine-mounted 

 slides, and which he says is glycerine proof. 



"Cox's gelatine, Jii ; acetic acid, fl. ^i ; gum 

 ammoniac, gr. x. Dissolve in a water bath, and 

 filter through cotton while warm. This cement 

 remains fluid when cold and dries quickly. After the 

 ring has become set or stiff, the whole slide is 

 immersed for a minute or so in a 10-grain solution of 

 bichromate of potash, and is then allowed to dry, 

 exposed to the light, which makes the bichromated 

 gelatine perfectly insoluble even in boiling water, and 

 thoroughly prevents the escape of any glycerine." 



This very ingenious method of employing bichro- 

 mated gelatine can be used for most fluid-mounted 

 preparations, and we have no doubt that where soft 

 balsam is used, it would form a very good foundation 

 for the coloured cements now so generally employed, 

 and effectually prevent their "running on." We 

 cordially recommend this journal to those interested 

 in microscopical studies, and advise all microscopical 

 societies to add it to their libraries. This work in 

 conjunction with the Transactions of our own Royal 

 Microscopical Society will keep the members posted 

 up in the latest microscopic news. — F. K., F.R.M.S. 



EUGLENA VIRIDIS AND HYDRATINA SeNTA.— 

 Your answer to M. H. Robson anent the Euglena 

 viridis leads me to mention the following circum- 

 stance. A little while ago, I obtained a sample of 

 water from a pond literally green with swarms of 

 what was, to all appearance, the Euglena viridis. 

 Careful examination of them, however, engendered 

 a doubt in my mind as to their identity with the true 

 Euglena, for I discovered that the flagellum was in 

 each case bulbed. I put the water aside for about a 

 week ; on again examining the objects, I was rather 

 surprised to find that the Euglena (?) had nearly all 

 disappeared, their place being taken by the common 

 Funnel Rotifer {Hydratina scnia) in various stages 

 of development. This circumstance seemed to con- 

 firm my previous suspicion, and favoured the notion 

 that the objects first observed were not the true 

 Euglena viridis, but were the larvae of the Hydratina 

 senta. Has Mr. Robson or others noticed any such 

 metamorphosis in the specimens ? If so, will not 

 the bulb serve as a feature whereby to distinguish the 

 true Euglena from other objects of similar shape and 

 colour ? — F. J as. George. 



The Fur on the Tongue.— A singularly in- 

 teresting paper has been read before the Royal 

 Society, by Mr. H. Trentham Butlin, F.R.C.S., on 

 the above subject, in which he showed that the so- 

 called " fur" is in a great measure due to the glcea of 

 certain forms of microscopical fungi. In order to 

 ascertain the true nature of glcea, and to obtain it in 

 a purer form, it was cultivated upon a warm stage. 

 Several fungi were then discovered, but only two 

 kinds were present in every experiment, viz., Micro- 



coccus and Bacillus subtilis. As the glcea produced 

 artificially was similar to that existing naturally in the 

 tongue fur, Mr. Butlin believes that "fur" is com- 

 posed essentially of these two fungi. Micrococcus 

 developed freely and abundantly, forming large 

 masses of yellow or brownish-yellow colour. Bacillus 

 did not develop, but existed in greater or less abun- 

 dance in all the cases examined. Mr. Butlin thinks 

 that one cause of its artificial non-development may 

 be the presence of other developing organisms, and 

 that development takes place freely upon the tongue. 

 Its habitual occurrence there, and the presence ot 

 spore-bearing filaments favour this view. Besides 

 the above, other fungi were present, as Bacterium 

 termo, Sarcina venlriculi, Spirochceta plicatilis, 

 Spirillum, etc. 



On Cleaning old Slides mounted in Balsam. 

 — Having seen a great deal lately about cleaning old 

 slides in your columns, it has occurred to me that 

 the method I use might be serviceable to some. The 

 process is as follows : I first heat the slide over a 

 spirit-lamp until the balsam is soft, then I scrape the 

 covering glass off, and as much balsam as possible. 

 I let it dry and chip off all I can with an old knife ; 

 and when I have taken it off, I soak a rag in tur- 

 pentine and rub the slide well with it (renewing the 

 turpentine when necessary) until all .the balsam i's 

 removed, which it is in a very short time. — H. C. 

 Bristowc. 



ZOOLOGY. 



Nocturnal Song of Birds. — There have 

 appeared from time to time in Science-Gossip 

 inquiries concerning birds singing by night. On the 

 third of last month (May) a thrush was heard singing 

 long and loud after 10 P.M. a little way out of this 

 town, on the Tring Road. — J. W. Slater, Aylesbury. 



Aerating Aquaria. — Dr. Lenz, of Lubeck, has 

 devised a method of aerating the water in an aquarium. 

 A tube conducting the air to the bottom is expanded 

 at the end and stuffed with fine sponge, which causes 

 the air to rise through the water in very minute 

 bubbles. 



The "Science Index." — We have received the 

 first part of a new publication bearing the above 

 name. It is edited by Mr. A. Hildebrandt, and pub- 

 lished in Manchester, and professes to^be a " monthly 

 guide to the contents of the scientific periodicals." 

 Such a work is much needed, and the "Science 

 Index " promises to fulfil the duty well, in spite of 

 some errors in the first part, which are evidently due 

 to the haste with which it has been got out. 



Male Eels. — In the " American Naturalist " for 

 May, Professor Packard announces the discovery of 

 male eels. At first they were supposed to be imma- 

 ture females, but the question is now finally settled, 



